U.S. patent application number 15/175251 was filed with the patent office on 2016-12-15 for display device.
The applicant listed for this patent is Japan Display Inc.. Invention is credited to Jun FUJIYOSHI, Yasukazu KIMURA, Takuma NISHINOHARA.
Application Number | 20160365523 15/175251 |
Document ID | / |
Family ID | 57516091 |
Filed Date | 2016-12-15 |
United States Patent
Application |
20160365523 |
Kind Code |
A1 |
NISHINOHARA; Takuma ; et
al. |
December 15, 2016 |
DISPLAY DEVICE
Abstract
A display device includes a first organic layer, a first
inorganic layer, a second organic layer, a second inorganic layer,
and a thin film transistor. The first organic layer has a roughened
top surface. The first inorganic layer has a roughened top surface
and is disposed to have a roughened bottom surface that is in
contact with the roughened top surface of the first organic layer.
The second organic layer has a roughened bottom surface that is in
contact with the roughened top surface of the first inorganic
layer. The second inorganic layer is disposed to be in contact with
the top surface of the second organic layer. The thin film
transistor is disposed on the top surface of the second inorganic
layer.
Inventors: |
NISHINOHARA; Takuma; (Tokyo,
JP) ; KIMURA; Yasukazu; (Tokyo, JP) ;
FUJIYOSHI; Jun; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Japan Display Inc. |
Tokyo |
|
JP |
|
|
Family ID: |
57516091 |
Appl. No.: |
15/175251 |
Filed: |
June 7, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/529 20130101;
Y02E 10/549 20130101; H01L 27/1262 20130101; H01L 51/5275 20130101;
H01L 51/5237 20130101; H01L 51/0097 20130101; H01L 51/5253
20130101; H01L 27/1218 20130101; H01L 2251/5338 20130101; H01L
27/3262 20130101; H01L 27/3248 20130101 |
International
Class: |
H01L 51/00 20060101
H01L051/00; H01L 51/52 20060101 H01L051/52; H01L 27/32 20060101
H01L027/32; H01L 27/12 20060101 H01L027/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 12, 2015 |
JP |
2015-119249 |
Claims
1. A display device comprising: a first organic layer having a
roughened top surface; a first inorganic layer having a roughened
bottom surface and a roughened top surface following the bottom
surface, the bottom surface being in contact with the roughened top
surface of the first organic layer; a second organic layer having a
roughened bottom surface in contact with the roughened top surface
of the first inorganic layer; a second inorganic layer in contact
with a top surface of the second organic layer; and a thin film
transistor above the second inorganic layer.
2. The display device according to claim 1, wherein the first
organic layer has a bottom surface opposite to the roughened top
surface thereof, and a protective layer formed of a resin is
disposed on the bottom surface of the first organic layer.
3. The display device according to claim 1, wherein the first
organic layer has a bottom surface opposite to the roughened top
surface thereof, a thermal diffusion sheet is disposed on the
bottom surface of the first organic layer, and a protective layer
formed of a resin is disposed on an opposite surface of the thermal
diffusion sheet from the bottom surface of the first organic
layer.
4. The display device according to claim 1, further comprising,
above the second inorganic layer: a lower electrode coupled to the
thin film transistor; a light-emitting layer on the lower
electrode; and an upper electrode on the light-emitting layer.
5. The display device according to claim 1, wherein the roughened
top surface of the first organic layer has a maximum height
roughness greater than or equal to 10 nm and less than or equal to
100 nm.
6. The display device according to claim 1, wherein the roughened
top surface of the first organic layer has an arithmetic mean
roughness greater than or equal to 1 nm and less than or equal to 5
nm.
7. The display device according to claim 1, wherein a plasma
treatment is applied to the top surface of the second organic
layer.
8. The display device according to claim 1, wherein the second
organic layer is formed by applying a varnish made of an organic
material to the roughened top surface of the first inorganic
layer.
9. A display device comprising: a substrate; an under film on the
substrate, the under film being made of an inorganic material; and
a thin film transistor on the under film, wherein the substrate has
a stack structure including a plurality of resin layers sandwiching
an inorganic layer therebetween, a resin layer in contact with the
under film, among the plurality of resin layers, has a first
surface located at a side of the under film and a second surface
opposite to the first surface, and the second surface is rougher
than the first surface.
10. The display device according to claim 9, wherein an outermost
layer which is located at an opposite side of the substrate from
the thin film transistor is one of the plurality of resin
layers.
11. The display device according to claim 10, wherein a protective
film formed of a resin is disposed on an opposite surface of the
outermost layer from the under film.
12. The display device according to claim 9, wherein the substrate
includes a first inorganic layer in contact with the second surface
and a first resin layer in contact with an opposite surface of the
first inorganic layer from the second surface, and a surface of the
first resin layer is rougher than the first surface, the surface
being in contact with the first inorganic layer.
13. The display device according to claim 9, wherein the substrate
is flexible.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from Japanese
application JP2015-119249 filed on Jun. 12, 2015, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to a display device.
2. Description of the Related Art
[0003] A display device having an under insulating layer
(underlayer) is conventionally known (e.g., FIG. 2 of JP
2015-079861 A). The underlayer functions as a barrier layer that
prevents moisture from entering a self-luminous element layer
including a light-emitting layer. In some cases, the underlayer is
formed by stacking an inorganic layer and an organic layer.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to prevent stacked
organic and inorganic layers in a display device from separating
from each other.
[0005] An aspect of the present invention includes a first organic
layer, a first inorganic layer, a second organic layer, a second
inorganic layer, and a thin film transistor. The first organic
layer has a roughened top surface. The first inorganic layer has a
roughened bottom surface that is in contact with the roughened top
surface of the first organic layer and a roughened top surface
following the bottom surface. The second organic layer has a
roughened bottom surface that is in contact with the roughened top
surface of the first inorganic layer. The second inorganic layer is
in contact with the top surface of the second organic layer. The
thin film transistor is disposed above the second inorganic
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a diagram schematically showing a general
structure of a display device according to this embodiment;
[0007] FIG. 2 is a cross-sectional view of an underlayer, which
schematically shows details of a stack structure of the
underlayer;
[0008] FIG. 3A is a process diagram for illustrating a process for
manufacturing the display device according to this embodiment;
[0009] FIG. 3B is a process diagram for illustrating the process
for manufacturing the display device according to this
embodiment;
[0010] FIG. 3C is a process diagram for illustrating the process
for manufacturing the display device according to this
embodiment;
[0011] FIG. 3D is a process diagram for illustrating the process
for manufacturing the display device according to this embodiment;
and
[0012] FIG. 4 is a diagram schematically showing a general
structure of a display device according to a modification of this
embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The following describes embodiments of the present invention
with reference to the accompanying drawings.
[0014] FIG. 1 is a diagram schematically showing a general
structure of a display device according to this embodiment. An
organic EL (electroluminescent) display device (hereinafter, simply
"display device") 100 according to this embodiment is a display
device that displays images on a display unit in which a plurality
of pixels are formed. As shown in FIG. 1, the display device 100
includes a self-luminous element layer 10, a sealing layer 20, an
underlayer 30, and a protective layer 40 (also referred to as a
protective film), which is formed by stacking them. The display
device shown in FIG. 1 is a flexible display device (flexible
display) in which a flexible resin substrate (film substrate) made
of, for example, a polyimide resin is used instead of a glass
substrate. The underlayer 30 shown in FIG. 1 includes this resin
substrate.
[0015] A stack structure of the self-luminous element layer 10 is
now described with reference to FIG. 1. The self-luminous element
layer 10 only needs to be a layer in which the brightness of
emitted light is controlled by each of a plurality of unit pixels
that form images, and is not limited to the structure shown in FIG.
1.
[0016] The self-luminous element layer 10 includes a self-luminous
light-emitting layer 11, a lower electrode 12 disposed on the
bottom surface of the light-emitting layer 11, and an upper
electrode 13 disposed on the top surface of light-emitting layer
11. In FIG. 1, the self-luminous element layer 10 also includes a
thin film transistor coupled to the lower electrode 12. That is,
the self-luminous element layer 10 includes insulating layers 14a
and 14b, a source-drain electrode 15, an insulating layer 16, a
gate line layer 17a, a polysilicon layer 17b, a source-drain region
18, and a bank 19 that are included in the thin film
transistor.
[0017] The lower electrode 12 is formed to cover a portion to be a
light-emitting area and is coupled to the source-drain electrode 15
through a through-hole in the insulating layer 14a. The bank 19 is
formed on the edge portion of the lower electrode 12 and over a
non-light-emitting area including the polysilicon layer 17b and the
gate line layer 17a. The light-emitting layer 11 is formed to cover
the lower electrode 12, but is separated from the lower electrode
12 by the bank 19 in the non-light-emitting area.
[0018] One of the lower electrode 12 and the upper electrode 13
functions as an anode, and the other functions as a cathode. When a
DC voltage is applied across the lower electrode 12 and the upper
electrode 13, holes injected from the anode reach the
light-emitting layer 11 via a hole transport layer (not shown),
electrons injected from the cathode reach the light-emitting layer
11 via an electron transport layer (not shown), and then the holes
and the electrons recombine there. The recombination of electrons
and holes causes the light-emitting layer 11 to emit light of a
certain wavelength.
[0019] The sealing layer 20 seals the self-luminous element layer
10 to prevent, for example, moisture from entering the
self-luminous element layer 10. The sealing layer 20 may be formed
of a dense inorganic layer such as silicon nitride or a film stack
including an inorganic layer and an organic layer. The sealing
layer 20 may include a color filter that absorbs light of a
specific wavelength and that passes light of other wavelengths
through itself. The underlayer 30 is disposed on the bottom surface
of the self-luminous element layer 10. The protective layer 40 is
made of an organic material, such as a polyimide resin or a
polyethylene terephthalate resin, and is disposed on the bottom
surface of the underlayer 30. The protective layer 40 may be
absent.
[0020] The following describes details of a stack structure of the
underlayer 30. FIG. 2 is a cross-sectional view of the underlayer
30, which schematically shows details of the stack structure of the
underlayer 30. The underlayer 30 has a structure in which at least
two organic layers (e.g., resin layers) and at least two inorganic
layers are alternately stacked on top of each other. Use of the
underlayer having such a stack structure provides improved barrier
properties compared with use of an underlayer having a single
structure including one organic layer and one inorganic layer that
are stacked, and prevents moisture from entering the self-luminous
element layer 10.
[0021] The underlayer 30 includes a first organic layer 31 (first
resin layer), a first inorganic layer 32, a second organic layer
33, and a second inorganic layer 34. As a material of the first
organic layer 31 and the second organic layer 33, a polyimide resin
or a polyethylene terephthalate resin may be used. As a material of
the first inorganic layer 32 and the second inorganic layer 34, for
example, silicon oxide or silicon nitride is used. Alternatively, a
moisture-resistant metal, such as titanium, may be used as a
material of the first inorganic layer 32 and the second inorganic
layer 34. It can be considered that the first organic layer 31
corresponds to a resin substrate used in the flexible display
instead of a glass substrate. Alternatively, it can be considered
that the first organic layer 31, the first inorganic layer 32, and
the second organic layer 33 are a substrate (also referred to as a
base material) of the flexible display with a plurality of organic
layers, and that the second inorganic layer 34 is an under film
disposed between the substrate and the thin film transistor.
[0022] The first organic layer 31 has a roughened top surface 31a
with projections and depressions. It is preferable that the
roughened top surface 31a of the first organic layer 31 has a
maximum height roughness greater than or equal to 10 nm and less
than or equal to 100 nm, and also has an arithmetic mean roughness
greater than or equal to 1 nm and less than or equal to 5 nm. The
maximum height roughness is the height from a reference level in
the thickness direction of the layer to the top of the projections
of the layer, and the arithmetic mean roughness is the mean value
of the heights of the projections from the reference level.
[0023] The first inorganic layer 32 has a roughened bottom surface
32b and a roughened top surface 32a. The bottom surface 32b is in
contact with the roughened top surface 31a of the first organic
layer 31. The roughened top surface 32a follows the bottom surface
32b.
[0024] The second organic layer 33 has a bottom surface 33b
roughened by its close contact with the roughened top surface 32a
of the first inorganic layer 32. The second inorganic layer 34 is
formed in close contact with the top surface 33a of the second
organic layer 33. Above the second inorganic layer 34, various
interconnections and a driver circuit including thin film
transistors are formed in addition to the self-luminous element
layer 10 shown in FIG. 1. As shown in FIGS. 1 and 2, for the second
organic layer 33, which is in contact with the second inorganic
layer 34, the bottom surface (second surface) 33b is rougher than
the top surface (first surface) 33a.
[0025] The underlayer 30 shown in FIGS. 1 and 2 has a structure
including two organic layers and two inorganic layers that are
alternately stacked on top of each other, but is not limited to
this structure. The underlayer 30 only needs to have a structure
including at least two organic layers and at least two inorganic
layers that are alternately stacked on top of each other. Thus,
three or more organic layers and three or more inorganic layers may
be alternately stacked on top of each other.
[0026] The following describes a process for manufacturing the
display device 100 according to this embodiment with reference to
FIGS. 3A to 3D. FIGS. 3A to 3D are process diagrams for
illustrating a process for manufacturing the display device 100
according to this embodiment.
[0027] As shown in FIG. 3A, the roughened top surface 31a is first
formed by applying a plasma treatment to the top surface of the
first organic layer 31 so that the top surface has projections and
depressions. As the plasma treatment, for example, a nitrogen
plasma treatment or an oxygen plasma treatment may be applied. The
formation of the roughened top surface 31a is not limited to plasma
treatment. For example, nanoimprint technology may be used for
forming the roughened top surface 31a. The first organic layer 31
is formed on a support substrate (not shown), for example, made up
of a glass substrate. Then, after the self-luminous element layer
10 and other components shown in FIG. 1 are formed, the support
substrate is separated from the first organic layer 31 by a known
method. The first organic layer 31 may be formed by applying liquid
varnish on a glass plate or by using a solid film made of an
organic material.
[0028] Subsequently, the first inorganic layer 32 is formed on the
roughened top surface 31a of the first organic layer 31. As shown
in FIG. 3B, the top surface of the first inorganic layer 32 has
projections and depressions following the shape of the roughened
top surface 31a.
[0029] Next, as shown in FIG. 3C, the second organic layer 33 is
formed on the roughened top surface 32a of the first inorganic
layer 32. The bottom surface 33b of the second organic layer 33 is
roughened by close contact of the second organic layer 33 with the
roughened top surface 32a of first inorganic layer 32. On the other
hand, the top surface 33a of the second organic layer 33 is formed
substantially flat by applying a varnish made of an organic
material.
[0030] As shown in FIG. 3D, the second inorganic layer 34 is then
formed on the top surface 33a of the second organic layer 33. The
top surface 33a of the second organic layer 33 is substantially
flat, and thus the top surface 34a of the second inorganic layer 34
formed on the second organic layer 33 becomes substantially flat.
The top surface 34a of the second inorganic layer 34, which is
substantially flat, does not affect its close contact with the
self-luminous element layer 10 having a substantially flat bottom
surface, and thus allows the self-luminous element layer 10 to be
formed on its planarized surface.
[0031] After a plasma treatment is applied to the top surface 33a
of the second organic layer 33, the second inorganic layer 34 may
be stacked on the second organic layer 33. On close examination,
the inventors have found that applying a plasma treatment to the
top surface 33a of the second organic layer 33 so as not to roughen
the top surface 33a promotes adhesion between the second organic
layer 33 and the second inorganic layer 34. The top surface 33a of
the second organic layer 33 is not roughened, and thus the bottom
surface 34b and the top surface 34a of the second inorganic layer
34 are also not roughened.
[0032] After that, the self-luminous element layer 10 and the
sealing layer 20 are stacked on the second inorganic layer 34. The
protective layer 40 is then stacked on the bottom surface 31b of
the first organic layer 31. Thereby, the display device 100 shown
in FIG. 1 is completed. When the first organic layer 31 is formed
on the support substrate, the support substrate is separated, and
the protective layer 40 is then laminated to the bottom surface 31b
of the first organic layer 31. The protective layer 40 is the
outermost layer of the display device 100 according to this
embodiment.
[0033] As shown in FIG. 4, a thermal diffusion layer 50 may be
provided between the first organic layer 31 and the protective
layer 40. The thermal diffusion layer 50 thus provided allows
temperature distribution to disperse, thereby preventing part of
the display device from generating an excessive heat. The
protective layer 40 and the thermal diffusion layer 50 shown in
FIGS. 2 and 4 are not essential to the present invention. The first
organic layer 31 may be the outermost layer of the display device
100.
[0034] An underlayer having a structure in which two organic layers
and two inorganic layers are alternately stacked on top of each
other increases the risk of layer separation because the interface
of the organic layers and the inorganic layers increases. However,
in this embodiment, a structure in which the first organic layer 31
and the first inorganic layer 32 are in close contact with each
other on their roughened surfaces and in which the first inorganic
layer 32 and the second organic layer 33 are in close contact with
each other on their roughened surfaces improves adhesion at the
interface between each pair of layers, thus making layer separation
less likely to occur. In addition, a plasma treatment is applied to
the top surface 33a of the second organic layer 33, and the second
inorganic layer 34 is then brought into close contact with the top
surface 33a. Consequently, improved adhesion at the interface
between the second organic layer 33 and the second inorganic layer
34 is provided, thus making layer separation less likely to
occur.
[0035] The first organic layer 31, the first inorganic layer 32,
and the second organic layer 33 each have projections and
depressions on its one or both surfaces. Accordingly, internal
stresses in these layers are reduced. In particular, applying the
structure according to this embodiment to a flexible display
device, which allows an image display unit to be flexibly curved,
produces the effects of improving the flexural strength of each
layer and of making the layers less likely to separate from each
other.
[0036] While there have been described what are at present
considered to be certain embodiments of the invention, it will be
understood that various modifications may be made thereto, and it
is intended that the appended claims cover all such modifications
as fall within the true spirit and scope of the invention.
* * * * *